Food Protection Trends - November/December 2017 - 400

from a local retailer as controls) were considered dirty
and failed the ATP test. In addition, heterotrophic plate
counts were tested as an overall indicator of the quality
of water that had been in the water bottle. According
to Allen, Edberg, & Reasoner (2), the number of HPC
bacteria in drinking water varies widely, and it is not
surprising that different countries establish different
upper HPC limits in drinking water. The Netherlands,
Sweden, and Germany have set a regulation of 100 CFU/
mL for drinking water (3). The maximum HPC level of
bottled water legally permitted in Taiwan is 200 CFU/
mL (33). The microbiological standard of bottled water in
Massachusetts in the United States follows a guideline of
500 CFU/mL for HPC (21). The HPC results of the two
control bottles were less than 1 CFU/mL. Of the PBS-T
solutions collected from the interior surfaces of 90 water
bottles, 63 (70%) were above the limit of 100 CFU/mL,
60 (66.67%) were above 200 CFU/mL, and 54 (60%)
had a HPC result higher than 500 CFU/mL. Moreover,
coliform bacteria were also found on the interior surfaces
of respondents' water bottles. According to the standard
of microbiological quality established by FDA (15) for
total coliforms in bottled water, coliform counts shall
not exceed 1 CFU/100mL. Of the 90 samples analyzed
for total coliforms, 21 (23.33%) contained more than 1
CFU/100mL. Four samples were reported with coliform
counts greater than 150 CFU/100mL.
While microbial counts were not determined for exterior
bottle surfaces, ATP levels suggest these surfaces may serve
as fomites that facilitate the transmission of infectious
organisms (36). The data clearly demonstrate that the
exterior cleanliness of reusable water bottles is associated
with bottle materials. As this study showed, among the four
bottle materials examined (hard plastic, soft plastic, metal,
and glass), glass bottles have the lowest reading of organic
residue on the exterior surface. This might be attributed
to the fact that glass is nonporous and easy to clean, but
perhaps more importantly, it is easy to see when it is
sufficiently clean, compared to plastic or metal bottles.
The exterior cleanliness of reusable water bottles was also
affected by the frequency of bottle use per week and the
frequency of bottle refilling per day. Generally speaking,
more frequent bottle refilling was associated with higher
levels of contamination. Possible reasons include that
each time people refill the bottle, the bottle might touch
a dispenser or have it drip onto the outside of a bottle,
providing a good source of moisture and nutrients for the
growth of microorganisms. A bottle owner's hands could
also be a source of contamination. Even if people wash
their hands on a regular basis, these uncleaned surfaces may
potentially re-contaminate hands and thus cause health
issues, especially with use of those bottles with a straw
or nozzle that require touching the drinking surface with
fingers in order to open and close it.
400
Food Protection Trends November/December
Moreover, the results obtained for bottle usage behaviors
show that the interior cleanliness of water bottles is affected
by different types of beverage. Bottles that had beverages
such as coffee/tea and soda in the past seven days were
found to be more contaminated than bottles that had only
water. This might be partially due to the fact that coffee and
tea leave residues that are hard to remove from food-contact
surfaces, and that soda contains sugar, which cannot be
removed easily by rinsing. Although studies have shown
that caffeine at high or low concentrations was effective at
inhibiting several strains of bacteria (1, 28), the sugar and
cream that may be added to coffee and tea could provide
nutrients for bacterial growth. A study that tested microbial
contamination in unfinished beverages, including coffee
with milk, green tea, apple juice drinks, and carbonated
drinks, found that pH, temperature, additives or ingredients
(such as carbon dioxide) are important for microbial
growth in beverages. The same study found that unfinished
beverages support microbial growth and can contain
foodborne pathogens and bacterial toxins (39). Bacterial
cells are more likely to adhere to and interact with surfaces
that are improperly cleaned and sanitized (5). It is possible
that residual nutrients are the cause of the attachment by
sugar and other additives. Moreover, coliform bacteria
are normal inhabitants of plant material such as tea leaves
(43). If tea is brewed at inadequate temperatures, or if it is
stored for too long or in an improperly cleaned container,
coliform bacteria may grow in it. In addition, bacteria grow
most rapidly in the range of temperatures between 40°F and
140°F, doubling in number in as little as 20 minutes (34). It
could be that the temperature of slowly cooling coffee/tea
could encourage bacterial growth. Therefore water bottles
which had coffee/tea/soda/energy drinks inside may have
been more susceptible to microbial contamination.
More than half (51.11%) of the respondents indicated
that they shared their bottles with others, a possible
cross-contamination risk. Researchers have suggested that
hundreds of bacteria species (around 700) exist in the
human oral cavity (8, 23). Harmful bacteria from saliva
will reproduce inside the bottle. When taking a drink,
reflux can occur into the liquid in the bottle, which is also
known as "backwash." Saliva not only provides the bacteria
for transmission but may also provide nutrients allowing
the microorganisms to multiply. In the possibility of virus
transmission from saliva means that sharing water bottles
with someone else could potentially lead to health issues.
When the impact of people's cleaning behavior on
the interior bioburden of water bottles was examined, it
appeared that whether or not people rinsed/washed their
water bottles affected the contamination level. However,
factors such as cleaning frequency, last time of cleaning,
cleaning method, and whether behavior changed during
illness when sick were not predictive of contamination
levels. There are some possible explanations regarding